Describe the condition of the front drivers seat. Worn side bolster etc. Seat pretty much like new or whatever.

I might start with a compression check of that number one cylinder. Also turn the engine over with that injector removed. Any oil spraying out? Even idle the engine with the injector out and a safety face shield.

The number one injector could also have a broken spring or be seriously cruded up so it does not close properly. I might grab a used injector just to use as a test aid. Or have someone test the existing one.. A simple repositioning of two injectors is not adequate for your issue.

I am trying to suggest that whatever the odometer reading is on these cars is not to be taken too seriously. You got the car with 50K claimed miles. The chances are small that anyone driving that little would have invested in a vegetable oil system. Fifty K miles was only a 1500 mile per year average or so.

Anything is possible though but to judge a 123 cars overall milage the condition of the front seat is useful sometimes. Also in general you finding a rebuilt injector in the last cylinder is very uncommon in a low miles car. At your milage the steering wheels indicated appearance should also be like new.

To research what a new steering wheel looks like check the archives or post a picture of yours for members to evaluate. Also a picture of the driver side bolster of the seat by the door. A car with 80K miles now is different to consider service wise than one with about the normal expected miles. Of the four 123 cars I have I would not bet anything that any of them are an accurate indication of the odometers claim. Well maybe one and a slight chance of another one. Nothing I would bet on though. There are more reasons for the odometer readings to be inaccurate on the 123 diesel cars than any other car I can think of. It just makes it somewhat easier to have some known indication of total miles to determine what is probably wrong.

I was mentally leaning towards turbo seals until you described the first cylinder. Your description of issues and observations is better than some incidentally. This can really help at times.